I attended an online talk by Dr. Sepehr Mortaheb (Postdoctoral Researcher) on a topic that does not come up often enough in mainstream neuroscience discussions: how spaceflight and microgravity reshape the human brain. I went in curious. I came out thinking, "yeah, this overlaps way more with what we do in MRI/fMRI."
This post is based on my notes and what I remember from the talk. Any scientific insight here belongs to the speaker and the work he presented. I am just connecting the dots and reflecting on why this matters.
Why study the brain in space at all?
Spaceflight is basically a perfect stress test for the human nervous system.
Astronauts (or cosmonauts, as the Russian crews are called) are exposed to a mix of extreme conditions:
- Microgravity
- Fluid shifts in the body
- Radiation
- Isolation and confinement
- Distance from Earth
Among these, the talk suggested that microgravity appears to be a primary driver of brain-related changes, and MRI has emerged as one of the key tools to study them.
What fascinated me is that this is not just theoretical. We are talking about structural MRI, diffusion MRI, and resting-state/task fMRI, collected before and after space missions, sometimes with long-term follow-ups.
The most striking structural finding: the brain literally shifts
One of the most consistent observations reported was an upward shift of the brain inside the skull during prolonged exposure to microgravity.
This isn't subtle.
- Cerebrospinal fluid (CSF) redistributes
- Ventricles expand
- Cortical and subcortical structures get displaced
What really surprised me: ventricular expansion often does not return to baseline, even months or years after astronauts return to Earth.
That is wild. We are not just talking about temporary adaptation. These are long-lasting structural changes.
And yes, this has clinical relevance. The CSF redistribution increases pressure around the optic nerve, which is linked to vision problems observed in astronauts.
Vestibular system: when gravity disappears, your brain panics
Another big theme was the vestibular system.
On Earth, your brain constantly fuses signals from:
- Vestibular organs
- Vision
- Proprioception
In microgravity, that balance collapses.
The vestibular system becomes unreliable, which leads to:
- Motion sickness
- Balance problems
- Impaired gaze stability
fMRI results showed altered functional connectivity in vestibular-related brain networks after spaceflight. The brain does not just "switch off" vestibular input. It reweights sensory information, leaning more heavily on vision and other cues.
From a systems neuroscience perspective, this is adaptation in real time.
Sensorimotor and cognitive effects are not spared either
The talk didn't stop at balance.
There were also results showing changes in:
- Sensorimotor networks
- Resting-state connectivity
- Task-based cognitive performance, including spatial working memory
This part hit close to home for me. Spatial cognition, sensory integration, and functional connectivity are all things we casually analyze in fMRI, often assuming a relatively stable biological baseline.
Spaceflight reminds us: the baseline itself is plastic.
Fighting microgravity: countermeasures are still experimental
Naturally, the question came up: can we prevent or reverse these effects?
Some countermeasures discussed included:
- Lower body negative pressure
- Exercise protocols
- Centrifugation (artificial gravity)
- Neuromodulation techniques like TMS / tDCS
What stood out is that no single solution fully solves the problem. The brain adapts, but not always in ways we want, and not always reversibly.
"Space on Earth": simulating microgravity without leaving the planet
One clever part of this research is how scientists simulate microgravity on Earth:
- Head-down bed rest (HDBR)
- Parabolic flights
MRI studies during these simulations reproduce many of the same effects seen in astronauts:
- Brain upward shift
- Functional connectivity changes
- Cognitive performance differences
This is huge, because it allows controlled experiments with proper baselines, something that's nearly impossible in actual space missions.
Why this matters for MRI and fMRI research
Here is my personal takeaway.
This line of work forces us to confront a hard truth:
Brain structure, functional connectivity, and sensory integration are not fixed reference frames.
They depend on:
- Gravity
- Environment
- Sensorimotor statistics
If microgravity can reshape large-scale networks and anatomy, then our assumptions about "normal" brain organization are more fragile than we think.
For anyone working in fMRI analysis, modeling, or interpretation, this is a reminder to stay humble. Context matters. Physiology matters. And sometimes, the signal changes because the brain itself has changed.
A personal note on retinotopy and space neuroscience
My research at the Medical University of Vienna focuses on retinotopy—the mapping between the visual field and the visual cortex. It is a fascinating area that sits at the intersection of visual neuroscience, fMRI methodology, and brain organization.
Thinking about how microgravity might affect the visual system and its cortical representations is genuinely intriguing. How does the removal of gravity reshape the topography of visual processing? What happens to the retinotopic maps when astronauts and cosmonauts experience the dramatic sensory recalibration described in this talk? These are questions I would love to explore.
So if you are planning or coordinating any space neuroscience studies involving visual cortex mapping or retinotopy, consider this an open invitation to collaborate. I am in!
Credit where it's due
All scientific content summarized here is based on the talk "Space and the Brain: How does microgravity affect the brain's structure and function" presented by Dr. Sepehr Mortaheb. This talk was organized by ISMRM | British & Irish Chapter as part of their education series.